Android中实现循环滚动

实现的效果图如下：

可循环滚动，当触摸结束时，会自动滚动到被选中的位置，同时显示该选中项。

由于Gallery已经过时，所以决定使用HorizontalScrollView控件。

下面是布局文件activity_main.xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  

    xmlns:tools="http://schemas.android.com/tools"  

    android:layout_width="match_parent"  

    android:layout_height="match_parent" >  

  

    <HorizontalScrollView  

        android:id="@+id/horizontalScrollView"  

        android:layout_width="match_parent"  

        android:layout_height="wrap_content"  

        android:layout_centerHorizontal="true"  

        android:layout_centerVertical="true"  

        android:scrollbars="none" >  

  

        <LinearLayout  

            android:id="@+id/linearLayout"  

            android:layout_width="wrap_content"  

            android:layout_height="match_parent"  

            android:orientation="horizontal" >  

        </LinearLayout>  

    </HorizontalScrollView>  

  

    <View  

        android:layout_width="1dp"  

        android:layout_height="match_parent"  

        android:layout_centerHorizontal="true"  

        android:background="#000000" />  

  

</RelativeLayout>

以下为相对应的Activity,MainActivity.java

package com.example.hscrollcircle;  

  

import android.app.Activity;  

import android.graphics.Color;  

import android.os.Bundle;  

import android.view.Gravity;  

import android.view.MotionEvent;  

import android.view.View;  

import android.view.ViewGroup;  

import android.view.ViewTreeObserver;  

import android.widget.HorizontalScrollView;  

import android.widget.LinearLayout;  

import android.widget.TextView;  

import android.widget.Toast;  

  

public class MainActivity extends Activity {  

  

    private HorizontalScrollView horizontalScrollView;  

    private LinearLayout linearLayout;  

    // 滚动条的宽度  

    private int hsv_width;  

    // 总共有多少个view  

    private int child_count;  

    // 每一个view的宽度  

    private int child_width;  

    // 预计显示在屏幕上的view的个数  

    private int child_show_count;  

    // 一开始居中选中的view  

    private int child_start;  

  

    @Override  

    protected void onCreate(Bundle savedInstanceState) {  

        super.onCreate(savedInstanceState);  

        setContentView(R.layout.activity_main);  

        init();  

    }  

  

    /** 

     * 初始化控件及变量 

     */  

    private void init() {  

        horizontalScrollView = (HorizontalScrollView) findViewById(R.id.horizontalScrollView);  

        linearLayout = (LinearLayout) findViewById(R.id.linearLayout);  

        child_count = 12;  

        child_show_count = 9;  

        child_start = 6;  

    }  

  

    /** 

     * 给滚动控件添加view，只有重复两个列表才能实现循环滚动 

     */  

    private void initData() {  

        for (int i = 0; i < child_count; i++) {  

            TextView textView = new TextView(this);  

            textView.setLayoutParams(new ViewGroup.LayoutParams(child_width,  

                    ViewGroup.LayoutParams.MATCH_PARENT));  

            textView.setText("" + (i + 1));  

            textView.setGravity(Gravity.CENTER);  

            linearLayout.addView(textView);  

        }  

        for (int i = 0; i < child_count; i++) {  

            TextView textView = new TextView(this);  

            textView.setLayoutParams(new ViewGroup.LayoutParams(child_width,  

                    ViewGroup.LayoutParams.MATCH_PARENT));  

            textView.setText("" + (i + 1));  

            textView.setGravity(Gravity.CENTER);  

            linearLayout.addView(textView);  

        }  

    }  

  

    /** 

     * 实现滚动的循环处理，及停止触摸时的处理 

     */  

    private void initHsvTouch() {  

        horizontalScrollView.setOnTouchListener(new View.OnTouchListener() {  

  

            private int pre_item;  

  

            @Override  

            public boolean onTouch(View v, MotionEvent event) {  

                // TODO Auto-generated method stub  

                boolean flag = false;  

                int x = horizontalScrollView.getScrollX();  

                int current_item = (x + hsv_width / 2) / child_width + 1;  

                switch (event.getAction()) {  

                case MotionEvent.ACTION_MOVE:  

                    flag = false;  

                    if (x <= child_width) {  

                        horizontalScrollView.scrollBy(  

                                child_width * child_count, 0);  

                        current_item += child_count;  

                    } else if (x >= (child_width * child_count * 2 - hsv_width - child_width)) {  

                        horizontalScrollView.scrollBy(-child_width  

                                * child_count, 0);  

                        current_item -= child_count;  

                    }  

                    break;  

                case MotionEvent.ACTION_UP:  

                    flag = true;  

                    horizontalScrollView.smoothScrollTo(child_width  

                            * current_item - child_width / 2 - hsv_width / 2,  

                            horizontalScrollView.getScrollY());  

                    Toast.makeText(MainActivity.this,  

                            "" + (current_item % child_count),  

                            Toast.LENGTH_LONG).show();  

                    break;  

                }  

                if (pre_item == 0) {  

                    isChecked(current_item, true);  

                } else if (pre_item != current_item) {  

                    isChecked(pre_item, false);  

                    isChecked(current_item, true);  

                }  

                pre_item = current_item;  

                return flag;  

            }  

        });  

    }  

  

    /** 

     * 设置指定位置的状态 

     *  

     * @param item 

     * @param isChecked 

     */  

    private void isChecked(int item, boolean isChecked) {  

        TextView textView = (TextView) linearLayout.getChildAt(item - 1);  

        if (isChecked) {  

            textView.setTextColor(Color.RED);  

        } else {  

            textView.setTextColor(Color.BLACK);  

        }  

    }  

  

    /** 

     * 刚开始进入界面时的初始选中项的处理 

     */  

    private void initStart() {  

        final ViewTreeObserver observer = horizontalScrollView  

                .getViewTreeObserver();  

        observer.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {  

  

            @Override  

            public boolean onPreDraw() {  

                // TODO Auto-generated method stub  

                observer.removeOnPreDrawListener(this);  

                int child_start_item = child_start;  

                if ((child_start * child_width - child_width / 2 - hsv_width / 2) <= child_width) {  

                    child_start_item += child_count;  

                }  

                horizontalScrollView.scrollTo(child_width * child_start_item  

                        - child_width / 2 - hsv_width / 2,  

                        horizontalScrollView.getScrollY());  

                isChecked(child_start_item, true);  

                return false;  

            }  

        });  

    }  

  

    /** 

     * 只有到了这个方法才能获取控件的尺寸 

     */  

    @Override  

    public void onWindowFocusChanged(boolean hasFocus) {  

        // TODO Auto-generated method stub  

        super.onWindowFocusChanged(hasFocus);  

        hsv_width = horizontalScrollView.getWidth();  

        int child_width_temp = hsv_width / child_show_count;  

        if (child_width_temp % 2 != 0) {  

            child_width_temp++;  

        }  

        child_width = child_width_temp;  

        initData();  

        initHsvTouch();  

        initStart();  

    }  

  

}